The invention discloses a process and a device for determining the activity of enzymes in liquids, or the concentration and/or activity of inhibitors in liquids.
The determination of enzyme activities in extracts of plants, suspensions of bacteria, homogenates and body fluids such as blood serum, blood plasma, urine, punctate, liquor, cell lines or homogenated tissue has obtained an essential importance for diagnosis, follow up and therapy control.
For example, the discrimination between enzyme proteins and the other proteins in blood serum by chemical means is exceedingly questionable, because the concentrations of the individual enzymes in body fluids are extremely small. The concentration of glutamate-oxaloacetate transaminase in blood serum of a healthy individual is 0,1 .mu.g/ml, for example. As for comparison, the total protein concentration in blood serum is in the range between 60 to 80 mg/ml, that is, the ratio of these two concentrations is about 1:700.000. Since the determination of the enzyme concentration by chemical means is questionable, the activity of the enzyme is calculated from the rate of its reaction with a suitable substrate.
The so called ELISA assay is known from clinical chemistry. This immunoassay measures the concentration of an enzyme and its corresponding enzym-inhibitor complex present in a tissue or any other sample. Measuring the enzyme activity by this method is impossible, as it measures concentrations regardless to the actual status of the enzyme, active or inhibited.
According to known techniques the activity of an enzyme is measured in such cases by removing at first the enzyme inhibitors corresponding to the enzyme and afterwards determining the activity of the enzyme. The known processes are very laborious, referring to the samples to be measured being tissues as well as to the method, how to remove the enzyme inhibitors from the sample. This method comprises adding to the sample a substance capable of binding the enzyme inhibitors, incubating the so manipulated sample during a definite time to complete the binding of the enzyme inhibitors along with as much homogenous mixing as possible of the sample with the said substance and finally, separating the so manipulated sample from the said substance.